Skip dependency install in cypress-io/github-action

The action was trying to use yarn with the yarn.lock file, which
has syntax errors. Since we already installed dependencies with
npm install --legacy-peer-deps in the previous step, we can skip
the install by setting install: false.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: davdhacs

.github/workflows/PR.yaml

@@ -243,6 +243,7 @@ jobs:
         uses: cypress-io/github-action@v6
         with:
           working-directory: go/src/github.com/stackrox/infra/ui
+          install: false
           start: npm run start
           wait-on: 'http://localhost:3001'
           wait-on-timeout: 60